1. Field of the Invention
This invention relates to interconnect, passive component and packaging structures for use primarily in conjunction with microwave enclosures with internal interconnects and microwave passive components and a method of fabricating such interconnect, component and packaging structures.
2. Background and Brief Description of the Prior Art
Single and multiple device RF packaging is typically characterized by a separate package into which devices, subassemblies and interconnects are mounted. Since the interconnects are not integrated into the package, there is a resulting size and performance loss. Characteristically, a RF interconnect is in an open microstrip configuration and shares an interconnect layer with power and other interconnects. Extra space is therefore required and RF isolation is compromised. This is increasingly true in the case of functions with complex interconnect requirements which cannot be easily packaged with the single level interconnect.
The dielectrics of choice are primarily polymer (organic) or ceramic (inorganic). These materials usually degrade thermal performance and provide RF leakage paths through their continuous layer.
The handling of individual microwave circuit packages individually increases the complexity of the manufacturing flow by requiring many individual setup actions, whether manual or automated. Also, the installation of hermetic feedthroughs in metal packages is expensive and requires additional interconnects during assembly. Ceramic packages further require soft mechanical interfaces to prevent breakage.
Many approaches to the problem of packaging and interconnect exist in the prior art, some of which are, in the case of hermetic packages, for example, a metal package with glass-to-metal seal or planar ceramic feedthroughs or a cofired ceramic package with single or multiple level interconnect. In the case of non-hermetic packages, there is, for example, a plastic package with a metal leadframe. The interconnect structure can be, for example, a thin film ceramic or Teflon (polytetrafluoroethylene) microstrip with wirebond or ribbon interconnect or a thickfilm multilayer for digital high density. However, these prior art approaches suffer from one or more of the above noted problems.
In the pursuit of improvements in the packaging techniques for microwave circuits, it must always be borne in mind that microwave frequencies require great precision in dimensioning and location of elements and demand specialized grounding configurations, thereby placing very severe restrictions upon the available procedures.